1. Field of the Invention
This invention relates to circuit interrupters which extinguish an electric arc by puffing an arc extinguishing fluid such as SF.sub.6 gas, and more particularly to circuit interrupters arranged to increase the pressure of the arc extinguishing fluid by the energy of the electric arc itself.
2. Description of the Prior Art
The self-extinguishing gas circuit interrupter which has been recently proposed comprises a pair of separable contacts disposed within an arc extinguishing chamber and a pressure chamber containing an arc extinguishing fluid such as SF.sub.6 gas, which pressure chamber is adapted to be highly pressurized by utilizing the energy of the electric arc established between the contacts and dissipated and transmitted to the surrounding extinguishing gas. The high pressure gas contained in the pressure chamber is released upon alleviation or reduction of the choking function based on a decrease in arc inner pressure or arc diameter, which rapidly decreases with a decrease in arc current, thereby extinguishing the arc by the arc extinguishing function of the continuing high pressure gas flow.
In this type of self-extinguishing gas circuit interrupter, it is critical to maintain the pressure of the arc extinguishing gas for a desired arc extinguishing function such as the arc diffusing or cooling function.
However, since the pressure increase of the arc extinguishing gas is obtained by heating the arc extinguishing gas so that it dissociates or expands by utilizing the high temperture of the generated arc, the arc extinguishing gas has a strong tendency to reach a high temperature as it becomes a high pressure gas, rendering the arc extinguishing gas to be less effective in extinguishing the arc.
More specifically, since the generated arc is unstable in its track and moves around within the arcing region and changes its form while it is arcing, the arc extinguishing gas within the arcing region is stirred by the hot high pressure gas generated by the moving arc and the stirred arc extinguishing gas flows into the pressure chamber in which the high pressure gas for arc extinction is stored, thereby disturbing or stirring the arc extinguishing gas within the pressure chamber. This stirring or disturbance of the gas promotes temperature diffusion, resulting in an increase of the temperature of the entire arc extinguishing gas within the arc extinguishing chamber, thereby degrading the arc extinguishing capabilities including the cooling, diffusing and insulating capabilities. Also, the turbulent flow within the pressure chamber remains until the high pressure is released thereby, disturbing the flow of the released gas to cause pressure loss, and also resulting in a decrease in arc extinguishing capability.